Polyphase synchronous alternators having a controlled voltage gradient armature winding

ABSTRACT

Polyphase synchronous alternators are described in which the armature conductors are wound to have a small voltage difference between most adjacent windings so that the conductors need to be insulated for this voltage. Regions of the armature winding where larger voltage differences exist are provided with additional insulation. The armature cross-section contains substantially more copper relative to insulation than the conventional machine because of the reduced volume of insulation thereby increasing the economic terminal voltage of the machine. A cryogenic field winding produces the required magnetic flux without requiring armature teeth in which the armature conductors are placed as in a conventional machine.

United States Patent [191 Smith, Jr. et al.

1 POLYPHASE SYNCHRONOUS ALTERNATORS HAVING A CONTROLLED VOLTAGE GRADIENT ARMATURE WINDING [75] inventors: Joseph L. Smith, Jr., Concord;

James L. Klrtley, Jr., Boston, both of Mass.

[73] Assignee: Massachusetts lnstltute of Technology, Cambridge, Mass.

[22] Filed: July 26, 1971 21 Appl. No.: 166,083

[52] US. Cl 310/198, 310/201, 310/205 [51] Int. Cl. H02k 19/00 [58] Field of Search .l 310/10, 40, 52, 198,

[451 July 3,1973

Primary EXam inerR. Skudy Attorney- Arthur A. Smith,Jr., Martin M. Santa et a1.

[5 7] ABSTRACT Polyphase synchronous altemators are described in which the armature conductors are wound to have a small voltage difference between most adjacent windings so that the conductors need to be insulated for this voltage. Regions of the armature winding where larger voltage differences exist are provided with additional insulation. The armature cross-section contains substantially more copper relative to insulation than the conventional machine because of the reduced volume of insulation thereby increasing the economic terminal voltage of the machine. A cryogenic field winding produces the required magnetic flux without requiring armature teeth in which the armature conductors are placed as in a conventional machine.

29 Claims, 42 Drawing Figures Patented July 3, 1913 3.143315 18 Sheets-$heet 1 INVENTORS JOSEPH L. SMITH, JR. JAMES L. KIRTLEY, JR.

ATTORNEY Patented July 3, 1973 3,743,815

18 Sheets-Sheet 2 INVENTOR5' JOSEPH L. SM'TH, JR, JAMES L. KIRTLEY, JR, BY A4 17.

ATTORNEY Patented July 3, 1973 3,743,815

18 Sheets-Sheet 5 JOSEPH L. SMITH, JR. JAMES -L. -KIRTLEY, JR.

mmi/4 ATTORNEY Patented July 3, 1973 18 Sheets-Sheet 4 Patented July 3, 1973 I 3,743,815

18 Sheets-Sheet 5 lNVENTORS JOSEPH L. SMITH, JR. JAMES L. KIBTLEY, JR.

BY LA:

ATTORNEY Patented July 3, 1973 18 Sheets-Sheet 6 fiH J3 QQKK.

O O O O 2' 4' I' 3' 3 2 4 FIG. I!

INVENTORS= JOSEPH L. SMITH JR. JAMES L. KIRTLEY, JR. BY ZJZ XM ATTORNEY Patented July 3, 1973 18 Sheets$heet 8 FIG. 22

FIG. 2|

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mm a H T mm 1-K L 1 H K N N a m M WO a T .JJVIA W B Patented July 3, 1973 3,743,815

18 Sheets-Sheet 9 8 C A 5 C' A 0 svws zywgveaw I ozoofe w sl'y .alo'wl k 03 I is I s": 'ggwwx FIG. 30

23 INVENTORS= JOSEPH LSMITH, JR.

ES L. KIRTLEY, JR.

ATTORNEY Patented July 3. 1973 3.743315 18 Sheets$heet 10 FIG. 25

jczics' m INVENTORS JOSEPH L. SMITH, JR. JAMES L, KIRTLEY, JR.

ATTORNEY Patented July 3, 1973 3,743,815

18 Sheets-Sheet 11 FIG. 26

' INVENTORS= JOSEPH L. SMITH, JR. JAMES L; I KIRTLEY, JR. BY zgut ATTORNEY Patented July 3, 1973 v 18 Sheets-Sheet 1B R oI , JR. JR

Y.. H Sm. K SL R .N O R ME 6 T EQYMZ VOA M v vB Patented July 3, 1973 18 Sheets-Sheet 15 mm wE INVE NTORS JOSEPH L. SMITH, JR. JAMES L. KIRTLEY,JR. Mi mi/ 41? ATTORNEY Patented July 3, 1973 18 Sheets-Sheet 14 mm mZu I m m INVENTORS was L. SMITH, JR. JAMES L. KIRTLEY, JR. Mimi ATTQRNEY Patented July 3, 1973 3,743,875

18 Sheets-Sheet 15 FIG-32 INVENTOR EP .SM|TH,JR. A ES IRTLEY, JR. BYZQ ATTORNEY Patented July 3, 1973 3,743,875

18 Sheets-Sheet 16 JOSEPH L. SMITH, JR. JAMES L. KIRTLEY,JR. BY -rcfl M ATTORNEY Patented July 3, 1973 3,743,815

18 Sheets-Sheet 17 Fl G 36 INVENTORS JOSEPH L. SMITH, JR. JAMES L. KIRTLEY, JR.

BY lwjl.

ATTORNEY Patented July 3, 1973 3,743,875

18 Sheets-Sheet 18 FIG. 37

INVENTORS JOSEPH L. SMITH, JR.

JAMES L. K!RTLEY, JR.

M1331. ATTORNEY POLYPHASE SYNCHRONOUS ALTERNATORS HAVING A CONTROLLED VOLTAGE GRADIENT ARMATURE WINDING This invention relates to polyphase synchronous alternators and in particular to alternator construction which allows terminal voltages at least several times the maximum economic voltage possible with conventional methods. This invention is particularly applicable to synchronous machines with super-conducting field windings although it may be used with conventional field windings.

In conventional synchronous machines, the required magnetic field can be obtained economically only if the magnetic circuit is high permeability iron except for the small air gap between the rotor and stator. When superconductors are used for the field winding, the magnetic field can be obtained economically without the aid of ferromagnetic material.

In the conventional machine the armature (stator) conductors must be placed in slots in the stator iron so that the air gap can be kept small. The magnetic flux then is concentrated in the iron teeth between the conductor bars. Since the magnetic iron of the armature must be at one electric potential and the armature conductors are at the A. C. terminal voltage of the machine (with the phase of the voltage different for each of the three phase windings), each conductor must be insulated for the full terminal voltage of the machine.

In the machine with superconducting field windings the armature conductors do not have to be set in slots in the armature iron. Therefore the conductors need to be insulated only for the voltage between adjacent conductors. Only the external insulation of the winding needs to withstand the full terminal voltage. This invention is the concept of arranging the armature winding in such a way that the voltage between adjacent bars is a minimum so that the total volume of insulation in the winding is a minimum for a given terminal voltage. Since the maximum terminal voltage of the machine is in simplest terms an economic optimization of the ratio of insulation volume to conductor volume, the reduction in the required volume of insulation increases the economic terminal voltage.

The voltage difference between conductors will be minimum when the voltage is distributed in a continuous wave around the central axis of the three phase winding. As an example, this condition of a continuous voltage wave exists when the windings are delta connected and the windings are formed by connecting the adjacent turns in series.

The previous discussion applies to the active central section of the armature winding there the conductors interact with the magnetic field and space is at a premium. In the end turn sections of the winding the conductors are spread out radially so that the winding becomes about twice as thick in the radial direction. This radial spread is necessary to provide space for the conductor to turn circumferentially from the axis of the machine to go around to the opposite side. End turn connections require that the conductors in some of the different layers of the end-turn sections of the winding must turn in opposite directions. End-tum layers are classed sub-layers. The voltage difference between the sub-layers in the end turns increases to full terminal voltage at the mid point of the end turn and then decreases to zero at the connectors at the extreme ends of the winding. The voltage difference between adjacent conductors in each sub-layer, however, remains low in the end turns. Thus, the end turns require additional insulation between sub-layers. This insulation can be provided by a cylindrical layer of insulation between the sub-layers of conductors which cross one another in the end turn region. This additional insulation in the end turns is not serious since the end turns are not in the main magnetic field and space for conductors is not at such a premium.

It is, therefore, an object of this invention to provide an alternator which will provide terminal voltages which are several times those economically possible in conventional alternators.

It is a feature of this invention that an armature is provided which has a controlled voltage gradient between its turns. It is a further feature of this invention that the active copper conductor occupies a greater fraction of the armature volume than in conventional machines because the armature conductors are not set in slots in the iron of the armature magnetic field structure and thus, do not require full terminal voltage insulation surrounding each conductor.

Other objects, features and advantages of this invention will become apparent from the following description taken in conjunction with the accompanying drawings in which:

FIG. 1 is a perspective view of one embodiment of the armature of this invention.

FIG. 2 is a cross-sectional view of the armature of FIG. 1 taken in the active region.

FIGS. 3 and 6 are cross-sectional views of the armature conductor bars taken at the ends of the active region.

FIGS. 4 and 7 are cross-sectional views of the bars of FIGS. 3 and 6 respectively after they have been formed into sublayers.

' FIGS. 5 and 8 are views of the sublayer bars showing their connections to each other at each end of the armature.

FIG. 8A is a conventional representation of a three phase, two pole, two layer armature winding.

FIGS. 9 and 10 are alternate representations of the bar arrangements of FIGS. 4, 5, 7 and 8 respectively.

FIGS. 11 and 12 show alternate end connections of the armature bars to that of FIGS. 9 and 10.

FIGS. 13 and 14 show other alternate end connections of the armature bars to that shown in FIGS. 9 and 10.

FIGS. 15 and 16 show still another alternate end connection of the armature bars other than that of FIGS. 9 and 10.

FIGS. 17 and 18 show the sublayer bar end connections for an armature having only a single layer in its active region.

- FIGS. 19 and 20 show the sublayer bar end connections for an armature having four layers in its active region.

FIGS. 21 and 22 show the phase connection diagrams for a delta and wye connection, respectively, of the armature phases.

FIG. 23 is a cross-sectional view of the armature showing insulating segments between the phase belts required when the wye connection of phases is used.

FIG. 24 shows the inter-layer insulation required between layers of bars in a two layer armature for an ar- 

1. An armature having a controlled voltage gradient winding comprising a plurality of electrically conductive bars, each bar being serially connected to a bar 180 electrical degrees removed therefrom to form a turn, turns adjacent to each other in the active region of the armature being serially connected to form a phase winding, said adjacent turns being without intervening electrically conductive material constituting the sides of slots in an iron armature, each turn being insulated to withstand substantially only the voltage difference between it and adjacent turns, said voltage difference being determined by the number of serially connected turns between said turn and an immediately adjacent turn and being substantially less than the phase voltage of the machine, said bars being formed into helices near their ends to cause said bars to twist through 90 electrical degrees, said helically twisted bars being connected at their ends to oppositely helically twisted bars to form said serial connection of turns of adjacent bars, additional insulation capable of withstanding the full phase voltage being inserted where the oppositely twisted bars cross each other.
 2. The armature winding of claim 1 comprising in addition said bars forming at least two sublayers of bars in each end region of said armature, the bars which are helically twisted in one direction at one end being in one sublayer and those bars which are helically twisted in the opposite direction being in a different sublayer, a bar of one sublayer being serially connected to a bar of a different sublayer to form a turn, adjacent sublayers which are oppositely twisted having said additional insulation in the form of a cylinder therebetween capable of withstanding the full phase voltage.
 3. The armature winding of claim 1 comprising in addition a plurality of N of said phase windings, the bars of one phase winding being insulated from the adjacent bars of the adjacent phase winding by no more insulation than that provided on each other bar of the phase windings, said phase windings being connected to a different phase winding at each end to form a balanced N-phase polygon connected armature winding.
 4. The armature of claim 3 wherein the plurality of phase windings is three in number and said balanced three-phase winding is delta connected.
 5. The armature winding of claim 1 comprising in addition a plurality of N of said phase windings, each phase winding being connected to a common terminal by one end of the phase winding to form a balanced N-phase star-connected armature winding, an insulator capable of withstanding the phase voltage being between adjacent phase windings.
 6. The armature winding of claim 5 wherein the plurality of phase windings is three in number and said balanced three-phase winding is wye connected.
 7. The armature winding of claim 2 comprising in addition said insulated bars substantially filling the space the active region of the armature.
 8. The armature winding of claim 1 comprising in addition a cylinder of insulation within said armature winding on which said winding is supported, a cylinder of insulation outside and surrounding said armature winding, each cylinder of insulation being capable of withstanding the phase voltage potential difference.
 9. The armature of claim 8 comprising in addition a cryogenic magnetic field structure located within and capable of rotating about the longitudinal axis of the armature, an electrically conductive cylinder having its axis coincident with the axis of the armature, said conductive cylinder being external to said armature and separated therefrom to provide an eddy current shield to prevent flux from said magnetic field structure and said armature extending beyond said cylinder.
 10. The armature of claim 8 comprising in addition a magnetic field structure located within and capable of rotating about the longitudinal axis of the armature, a cylinder of ferromagnetic material having its axis coincident with the axis of the armature, said magnetic cylinder being external to said armature to provide a magnetic return path for the flux produced by said magnetic field structure and said armature.
 11. An armature winding comprising 2N phase belts, where N is one or greater, each phase belt comprising ''''n'''' electrically conductive bars arranged cylindrically in two layers with the bars of the outermost layer being radially displaced from the bars of the innermost layers, the bars of a first phase belt being consecutively numbered with the outermost bar at one end of the phase belt being designated with the numeral one and the bar radially displaced therefrom being designated with the numeral two, the last bar of the belt being the innermost bar at the other end of the belt which is designated ''''n'''', a second phase belt displaced from said first phase belt by 180 electrical degrees, corresponding bars of the first and second phase belts being correspondingly numbered, the bar numbers being primed in the second phase belt to distinguish these bars from those of the first phase belt, said phase belts having a non-terminal end at which the bars of the first and second belts are connected to form turns and a terminal end at which the turns are serially connected to form a phase winding, said 2N phase belts each having their corresponding bars numbered to correspond with each other, alternate belts having primed numbers, said bars being insulated from each other to withstand the voltage difference between adjacent bars, said bars being without intervening electrically conductive material constituting the sides of slots in an iron armature.
 12. The armature winding of claim 11 comprising in addition the order of connection of the bars of the two phase belts at the non-terminal end being 1-1'', 2-2'', - - - , n-n'', the order of connection of the bars of the two phase belts at the terminal end being 1''-2, 2''-3, - - - , (n-1)''-n, said connections providing a sequence of connections of the bars in any one phase of 1-1''-2-2''-3-3'', - - - , (n-1)-(n-1)''-n-n'' to provide a phase winding between the terminal ends of bars 1 and n'', said 2N phase belts thereby providing N phase windings, said bars being insulated from each other to withstand substantially three turns of voltage.
 13. The armature winding of claim 12 comprising in addition said N phase windings being three in number, said three phase windings being connected to each other at the terminal end of the phase windings to form a delta connected balanced three phase armature winding by connecting terminal one of one phase winding to terminal n'' of the adjacent phase winding, the phase belts having no additional insulation other than the said bar insulation between them where they are next to each other.
 14. The armature winding of claim 12 comprising in addition said N phase windings between three in number, said three phase windings being connected to each other at the terminal end of the phase windings to form a wye connected balanced three phase armature winding by connecting together terminal n'' of each phase winding, the phase belts being separated by insulation capable of withstanding the full phase voltage.
 15. The armature winding of claim 11 comprising in addition the order of connection of the bars of the two phase belts at the non-terminal end being 1-2'', 1''-2, - - - , (n-1)''-n, the order of connection of the bars of the two phase belts at the terminal end being 1''-4, 2-2'', 3-3'', 4''-5, - - - , (n-1)-(n-1''), said connections providing a sequence of connection of the bars in any one phase of 1-2''-2-1''-4-3''-3-4''-5, - - - (n-1)-n'' to provide a phase winding between the terminal ends of bars 1 and n'', said 2N phase belts thereby providing N phase windings, said bars being insulated from each other to withstand substantially three turns of voltage.
 16. The armature winding of claim 15 comprising in addition said N phase windings being three in number, said three phase windings being connected to each other at the terminal end of the phase windings to form a delta connected three-phase armature winding by connecting terminal one of one phase winding to terminal n'' of the next phase winding.
 17. The armature winding of claim 15 comprising in addition said N phase windings being three in number, said three phase windings being connected to each other at the terminal end of the phase windings to form a wye connected balanced three phase armature winding by connecting together terminal n'' of each phase winding, the phase belts being separated by insulation capable of withstanding the full phase voltage.
 18. The armature winding of claim 11 comprising in addition the order of connection of the bars of the two phase belts at the non-terminal end being 1-3'', 1''-3, 2-4'', 2''-4, - - - (n-2)''-n, the order of connection of the bars of the two phase belts at the terminal end being 1''-4, 2-3'', 3-4'', 2''-5, - - - , (n-1)-n'', said connections providing a sequence of connection of the bars in any one phase of 1-3''-2-4''-3-1''-4-2''-5 - - - n-(n-2)'' to provide a phase winding between the connected terminal ends of bars 1 and (n-2)'', said 2N phase belts thereby providing N phase windings,, said bars being insulated from each other to withstand substantially six turns of voltage.
 19. The armature winding of claim 18 comprising in addition said N phase windings being three in number, said three phase windings being connected to each other at the temminal end of the phase windings to form a delta connected three-phase armature winding by connecting terminal one of one phase winding to terminal (n-2)'' of the next phase winding.
 20. The armature winding of claim 18 comprising in addition said N phase windings being three in number, said three phase windings being cnnnected to each other at the terminal end of the phase windings to form a wye connected balanced three phase armature winding by connecting together terminal (n-2)'' of each phase winding, the phase belts being separated by insulation capable of withstanding the full phase voltage.
 21. The armature winding of claim 11 comprising in addition the order of connection of the bars of the two phase belts at the non-terminal end being 1-2'', 2-1'', 3-4'', 4-3'', - - - , n-(n-1)'', the order of connection of the bars of the two phase belts at the terminal end being 1''-4, 2''-3, 2-4'', 3''-5, - - - , (n-2)-n'', said connections providing a sequence of connection of the bars in any one phase of 1-2''-3-4''-2-1''-4-3'' - - - n-(n-1)'' to provide a phase winding between the connected terminal ends of bars 1 and (n-1)'', said 2N phase belts thereby providing N phase windings, said bars being inSulated from each other to withstand substantially four turns of voltage.
 22. The armature winding of claim 21 comprising in addition said N phase windings being three in number, said three phase windings being connected to each other at the terminal end of the phase windings to form a delta connected three phase armature winding by connecting terminal one of one phase winding to terminal (n-1)'' of the next phase winding.
 23. The armature winding of claim 21 comprising in addition said N phase windings being three in number, said three phase windings being connected to each other at the terminal end of the phase windings to form a wye connected balanced three phase armature winding by connecting together terminal (n-1)'' of each phase winding, the phase belts being separated by insulation capable of withstanding the full phase voltage.
 24. A winding for four-pole armature comprising an armature having two layers of electrically conductive bars in the active region of the armature arranged to provide 12 phase belts, said bars arranged to form an outermost layer of bars radially displaced from the bars of the innermost layers, the bars of a first phase A all being adjacent to each other and consecutively numbered with the innermost bar at one end of the phase belt being designated with the numeral one and the bar radially displaced outwardly therefrom being dsignated with the numeral two, the last bar of the belt being the outermost bar at the other end of the belt designated ''''n,'''' a second phase belt A'' displaced from said first phase belt A by 180 electrical degrees, the corresponding bars of the second phase belt being designated with primed numerals in the same order as said first phase belt bars, a third and fourth phase belt corresponding to said first and second phase belts, respectively, and displaced therefrom by 180 mechanical degress with bars corresponding to 1 to n being designated by the unprimed and primed numerals (n+1) to 2n, respectively, the electrical sequence of connection of the serially connected bars of the four phase belts being 1-2''-(n+1)-(n+2)'' - - -(2n-1)- (2n)'' connected in parallel with the serially connected bars 2-(n+1)''-(n+2)-1''-, - - - , -n-(2n-1)''-2n-(n-1)'', said connections providing a phase winding between the ends of bars 1 and (2n)'', the remaining eight of said 12 phase belts being likewise connected to each other to form two other phase windings, the three phase windings having correspondingly numbered bar 1 and (2n)'' ends 120 electrical degrees out of phase with each other, said bars being insulated from each other to withstand substantially three turns of voltage.
 25. The armature winding of claim 24 comprising in addition said three phase windings being connected to each other to form a delta connected balanced three phase armature winding by connecting terminal one of one phase winding to terminal (2n)'' of the next phase winding.
 26. A controlled voltage gradient armature winding for a two-pole machine comprising an armature having electrically conductive bars in the active region of the armature arranged to provide six phase belts, the bars of a first phase belt A being consecutively numbered with the endmost bar at one end of the phase belt being designated with the numeral one and the endmost bar at the other end of the phase belt being designated ''''n,'''' a second phase belt A'' displaced from said first phase belt A by 180 electrical degrees, the corresponding bars of the second phase belt being designated with primed numerals in the same order as said first phase belt bars, the electrical sequence of connections of the serially connected bars of the first anD second phase belts being 1''-2-3''-4 - - -(n-1)''-n connected in parallel with the serial connection of bars 2''-1-4''-3-n''-(n-1), said connections providing a phase winding between the ends of bars 1'' and n, the remaining four of said six phase belts being likewise connected to each other to form two other phase windings, the three phase windings having correspondingly numbered bars 1'' and n 120 electrical degrees out of phase with each other, said bars being insulated from each other to withstand substantially two turns of voltage.
 27. The armature winding of claim 26 comprising in addition said three phase windings being connected to each other to form a delta connected three phase armature winding by connecting terminal 1'' of one phase winding to terminal n of a different phase winding.
 28. A controlled voltage gradient armature winding for a four pole machine comprising an armature having two layers of electrically conductive bars in the active region of the armature arranged to provide twelve phase belts, said bars arranged to form an outermost layer of bars radially displaced from the bars of the innermost layers, the bars of a first phase belt A being consecutively numbered with the innermost bar at one end of the phase belt being designated with the numeral one and the bar radially displaced outwardly therefrom being designated with the numeral two, the last bar of the belt being the outermost bar at the other end of the belt designated ''''n,'''' a second phase belt A'' displaced from said first phase belt A by 180 electrical degrees, the corresponding bars of the second phase belt being designated with primed numerals in the same order as said first phase belt bars, a third and fourth phase belts corresponding to said first and second phase belts, respectively, and displaced therefrom by 180 mechanical degrees with corresponding bars being designated by the unprimed and primed numerals (n+1) to 2n, respectively, the electrical sequence of connection of the serially connected bars in the four phase belts being 1-1''-(n+1)-(n+1)''-2-2''-(n+2)-(n+2)'' - - - (2n-1)-(2n-1)''-n-n''-2n-(2n)'', said connections providing a phase winding between the ends of bars 1 and (2n)'', the remaining eight of said 12 phase belts being likewise connected to each other to form two other phase windings, the three phase windings having correspondingly numbered bar 1 and (2n)'' ends 120 electrical degrees out of phase with each other, said bars being insulated from each other to withstand substantially two turns of voltage.
 29. The armature winding of claim 28 comprising in addition said three phase windings being connected to each other to form a delta connected three phase armature winding by connecting terminal one of one phase winding to terminal (2n)'' of the next phase winding. 